LAGOS, Nigeria (AP) — A group that monitors piracy says well-armed pirates are using new strategies to hijack ships and widening their area of operations amid a “worrying surge” in attacks, kidnappings and armed robberies in West Africa’s oil-rich Gulf of Guinea.

The London-based International Maritime Bureau’s Cyrus Moody says in one attack pirates boarded a container ship and kidnapped the crew some 170 miles (274 kilometers) off the coast of Nigeria. He says it shows “a very different modus operandi” and “capacity to travel further distances.”

The bureau’s report published Monday says Nigeria suffered 22 actual and attempted attacks so far this year, up from six in 2011.